Homeostasis Flashcards
Homeostasis
Maintains constant internal environment
Necessary because enzymes need specific pH levels, temperatures and ion concentrations to work
Homeostatic Processes
Involve nerves and hormones
Keeps internal environment within tolerance limits
Control metabolism, and physiological and behavioural activities.
Hormones
Chemical messengers
Released from endocrine glands into blood plasma
Affect target organs
Positive Feedback
amplifies/reinforces original stimulus to maintain homeostasis
Negative Feedback
reduces effect or eliminates original stimulus in order to maintain homeostasis
Negative Feedback Cycle
- Stimulus
- Receptor
- Modulator
- Effector
- Response
- Feedback
Stimulus
Change to stable state
Receptor
Detects change
Modulator
Processes information and stimulates response
Effector
Effect of stimulus is counteracted
Response
Action of the Effector
Feedback
Steady state has been restored
Glycogenesis
The production of glycogen, mostly from glucose
Glycogen
Long strings of glucose molecules
Stored in the liver and skeletal muscles
Insulin
Pancreatic hormone
Stimulates glycogenesis
Decreases blood sugar levels
Secreted by beta cells
Glycogenolysis
Break down of stored glycogen into glucose
Glucagon
Pancreatic hormone
Stimulates glycogenolysis
Increases blood sugar levels
Secreted by alpha cells
Islets of Langerhans
Clusters of hormone-secreting cells within the pancreas
Two types of cells: alpha and beta
Alpha Cells
Type of cell in the Islets of Langerhans
Secrete glucagon
Beta Cells
Type of cell in the Islets of Langerhans
Secrete insulin
Adipose Tissue
Fat storing tissue
Gluconeogenesis
Process of creating glucose from substances other than stored glycogen, e.g., proteins
Adrenal Cortex
Outer part of the adrenal glands
Adrenal Medulla
Inner part of the adrenal glands
Glucocorticoids
Hormones secreted by adrenal cortex
Includes cortisol
Stimulate glycogenolysis
Increase the rate at which amino acids are brought to the liver for gluconeogenesis
Adrenaline
Hormone secreted by adrenal medulla
Increases blood sugar levels
Counteracts effects of insulin
Stimulates lactic acid production, which can then be converted into glucose
Blood Sugar Homeostasis
Contribution of the liver, adrenal glands and pancreas to keep blood glucose levels between 4 & 6 mmol/L
Chemoreceptors
Located in medulla oblongata (in brain)
Monitor blood sugar levels
Send messages to hypothalamus
Hypothalamus
Located at the base of the brain
Connected to pituitary glands by infundibulum
Contains two kinds of nerve cells, one set for the APG and the other for the PPG
Sends hormones to PPG to be secreted
Sends releasing/inhibiting factors to APG
Anterior Pituitary Gland
Pituitary gland in front
Secretes hormones, regulated by factors sent by hypothalamus
Connected to hypothalamus by blood vessels
Posterior Pituitary Gland
Gland behind
Secretes hormones sent to it
Does not create it’s own hormones
Connected to hypothalamus by nerves
Pineal Gland
Deep in brain
Secretes melatonin
Decreases in size after puberty
Stimulated by darkness
Adrenocorticotropic Hormone
Released by APG
Stimulates release of cortisol from adrenal cortex
Lipid-soluble Hormones
Steroid hormones
Slow acting, long lasting
Diffuse directly into cell
Bind to receptor protein, forming hormone-receptor protein complex
Complex binds to genes that code for specific proteins
Either inhibits or increases protein synthesis
Water-soluble Hormones
Peptide/amine hormones
Fast acting, don’t last long
Cannot cross cell membrane
Bind to receptor protein in cell membrane
Activates secondary messenger, which diffuses throughout the cell
Secondary messengers activate specific enzymes
Lipid Soluble Hormones to Know
Aldosterone
Cortisol
Known as corticosteroids
Infundibulum
Stalk connecting the hypothalamus to the pituitary gland
Phrenic Nerve
Stimulates diaphragm
Intercostal Nerve
Stimulates intercostal muscles
Restriction Enzymes
Enzymes used to cut sections of DNA
Specific to recognition sites
Sticky ends vs blunt ends
Sticky ends:
